[mythtv] HD Prebuffering Pauses on Frontend

[Chris Dos]

I've been discussing this problem on the users list, and I think that a change
SVN is causing my issues.

The summary of the problem is that HD playback seems to take a lot more CPU than
it use to, and it's causing prebuffering pauses.

I built a new frontend for Christmas.  It's spec's are:

AMD X2 3800+ proc running at 2.0 ghz
Asus M2NPV-VM MB with Integrated Geforce 6150 Video VGA/DVI
1 GB RAM
etc.

I'm currently using SVN 12356 for both the combo backend/frontend (which I will
refer to it as the backend) and the dedicated frontend.

The backend can still play back HD using libmpeg2 though at close to 85-90%
processor on one of cores.  It has a X2 4200+ proc running at 2.2ghz.  It use to
run at 40% for the frontend process and 35% for the xorg process.

The frontend is connecting to the backend via wireless 802.11a in turbo mode and
it can sustain 4 MB/s throughput.  Just in case it was the wireless causing
problem, I hooked up a long Cat5e cable running a Gigabit to see if it made any
changes, and it did not.

I'm running a stock 2.6.19 kernel on both the backend and frontend.  I'm using
the Nvidia driver 9629 on the backend, and I started with 9629 on the frontend,
and have since upgraded the frontend to 9746 and that didn't make any change.

So the backend can playback HD using libmpeg2 just barely, the frontend cannot.

I'm not using OpenGL vertical sync on either the backend of the frontend.

On a whim, I tried to set up XvMC on the frontend to get HD playback.  I haven't
had XvMC working for HD playback since 18.1, but low and behold, it's working
using XvMC.    Fantastic work there everyone!

Using XvMC I'm just getting a just perceptible little audio pop/crackle about
once a minute or so during playback.  I'll have to try and figure out that is
causing that.

So I don't mind using XvMC for the time being, but I did design this frontend to
be powerful enough to not have to use XvMC.

Talking on the IRC, it seems that a lot of people have seem CPU usage increase
for general usage, but some have not.